LU-8287 nodemap: don't stop config lock when target stops

LU-8287 nodemap: don't stop config lock when target stops

Target config log locks keep a reference to the global nodemap config
lock to ensure that it exists while the target is up. When a target
is unmounted, the cld_stopping flag on the config lock is set. The
nodemap lock, however, should not have its flag set as other targets
may still be active. The nodemap config lock is cleaned up when the
final target config lock is cleaned up.

This also changes nodemap so it revokes locks only when enabled.

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: Ibe32f82a6e1a08a011e3d1ede213a2a403befeb8
Reviewed-on: http://review.whamcloud.com/20954
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>